1. Field of the Invention
The present invention relates to a display method, a container, a carrying document, an adhesion strength measuring method, and a composite manufacturing method for resin material (resin composition), and more particularly to a display method, a container, a carrying document, an adhesion strength measuring method and a composite manufacturing method for resin material (resin composition) which is capable of providing a universal adhesion strength regardless of dimensions and configuration of adhering specimens, and further to a resin material (resin composition), the adhering reliability of which can be easily evaluated.
2. Description of the Related Art
In resin-molded electronic and electric parts containing inserting components such as resin encapsulated semiconductor devices and resin insulating transformers, the inter-faces between the resin and the inserting components are subjected to high residual stress due to cure shrinkage of the resin and thermal expansion mismatch between the resin and the inserting components.
Further, the internal exothermic action and the harsh heating/cooling operations increase the thermal stress which sometimes causes delamination during operations of the components and reliability tests.
Such a delamination at adhering interfaces not only results in corrosion of electric wiring materials and electric insulating degradation, but also causes a variety of other damages, such as cracking of the resin and wire breaking due to the stress concentration by the delamination.
The evaluation of resin material adhesion strength is therefore a critical issue in assuring the reliability of such resin-molded components.
Conventional methods for measuring the adhesion strength of resin material apply tensile or shear loads to an adhering specimen, and then divide the obtained fracture (delamination) loads by the adhesion area or length as described in IEEE Transactions on Comp., Hybrids, Manuf. Technol., Vol. 14, No. 4 (1991) pp. 809-817 and in Adhesion Technology, Vol. 9, No. 1 (1990) pp. 60-63 and 64-75.
Another method is disclosed in the Proceedings of the 67th Spring Annual Meeting of the Japan Society of Mechanical Engineers Ser. A (1990), pp. 75-77. In this method, a load is applied to an adhering specimen having partly formed delaminating portions, and a stress distribution near the delamination tip, i.e. near the boundary between the delaminating portion and the adhering portion, at the onset of delamination propagation is described by fracture mechanics parameter.
Further, other method is disclosed in the Transactions of the Japan Society of Mechanical Engineers, Ser. A, Vol. 54, No. 499 (1988) pp. 597-603. In this method, a temperature at which delamination takes place due to a residual stress is measured during cooling process after molding an adhering specimen, and a residual stress distribution at the delamination onset portion at that time is analyzed.
Among aforementioned conventional arts, in the tensile/shear loads applying method there is present the residual stress already when the adhering specimen is made. Therefore, the measurable adhesion strength would be nothing more than an apparent adhesion strength, which is a superimposition of the residual stress on the true adhesion strength.
Particularly in the case of semiconductor transfer molding resin for semiconductor encapsulation, the adhesion strength is relatively low due to a mold release agent contained in the resin material for easily parting from molding die. As a result, the reduction rate of the adhesion strength caused by the residual stress becomes large, such that the residual stress sometimes causes by itself the delamination at the interface.
Even if the adhesion strength measured by such a method is compared to an interface stress obtained by analysis or experiment, the adhering reliability of the resin molded components cannot be evaluated.
Further, the stress at the adhering interface is not uniform, but has singularity so as to become infinite at the end portions.
All the distributions of the residual stress and the stress caused by the load application during the adhesion test depend on the dimensions, shapes and materials of the specimens. Accordingly, in such conventional methods, as dividing the load by the adhering area on the assumption that the stress is uniformly distributed, dividing the load by the adhering length on the assumption that the load acts only on a line along the delamination front, the resulting adhesion strength depends on the dimensions, shapes etc. of the specimens, such that no universal measured value can be obtained.
If there is no residual stress, it is possible to obtain a universal adhesion strength by a method of describing a stress distribution near a singular point such as delamination tip by use of fracture mechanics parameters. On the other hand, however, in the case of the residual stress being present, the residual stress distribution must be obtained by analysis, as in the aforementioned last reference, the Transactions of the Japan Society of Mechanical Engineers, Ser. A, Vol. 54, No. 499 (1988) pp. 597-603. The analysis of the residual stress would be sometimes quite complicated or difficult to be performed with high accuracy due to conspicuous temperature dependency of the material properties or significant viscoelastic behavior at high temperatures depending on the materials of the resin composition.
Further, as in the case of the last reference, if the delamination is caused only by the residual stress, there would be a disadvantage that the adhesion strength may not be freely measured at any desired temperatures.
Thus, in the conventional methods, any universal adhesion strength as material property values could not be actually obtained. As a result, it is not possible to quantitatively predict the adhesion reliability of the interface of resin-molded products, such that the adhering state and adhesion strength etc. of the interface should be actually tested and measured by actually making the resin-molded products.